My cousins and i have a strong bond,?

im 14 and my cousins and i have a strong bond, my stepsisters and stepmom are trying to break that so that the two girls can replace me... my cousins and i have fought a fierce battle with the whole family about that and us three have a bad reputation because of us "excluding" them... were visiting them for turkey day and im running out of options and i dont want to give up..... how do i keep us together without them being apart of this.... pranks? revenge?